The outside of the nuclear bunker at Coswarth, near Newquay in Cornwall, which is expected to raise £50,000 when sold at auction. Photograph: South West Water/PA

A secret underground emergency bunker built to protect essential services in the event of a nuclear war is to go under the hammer. It was built in 1978 in Coswarth, near Newquay in Cornwall, during the cold war so that experts at the local water authority could maintain water and sewerage operations in the event of a nuclear attack.

The 3,000 sq ft bunker, which is on the market for £50,000, was designed for 16 people: seven in the operations room, six in the communications room and three in the control room. Other features include several blast-proof doors, an air lock, a decontamination room, a dining room, a recreation room and two dormitories.

Brian Blake, South West Water's asset performance manager, remembers the bunker from his time working for the South West Water Authority. "The government said we had to provide an underground control centre in case of emergency which was bomb and nuclear proof," he said. "It wasn't fully kitted out as there was no furniture in there, but if something had happened you could have lived in there for weeks."

Chris Shapland, South West Water's property manager, said: "We regularly auction redundant assets to reduce our costs and keep customers' bills as low as possible, but this is the first time we've offered a genuine piece of cold war history.

"Novelty sites with small areas of surplus land always attract strong interest as people are able to invest relatively modest sums for their 'little bit of England'.

"Several of our former storage reservoirs and pumping stations have been converted by their new owners into unusual homes. It will be interesting to see what happens to the bunker - you never know who could end up using it."